NoMethodError: undefined method `username' for nil:NilClass - Unable to Invite by Email Address
https://sentry.gitlab.net/gitlab/gitlabcom/issues/648748/
NoMethodError: undefined method `username' for nil:NilClass
members/create_service.rb:26:in `block in execute'
errors << "#{member.user.username}: #{member.errors.full_messages.to_sentence}"
members/create_service.rb:24:in `each'
members.each do |member|
members/create_service.rb:24:in `execute'
members.each do |member|
gitlab/metrics/instrumentation.rb:161:in `block in execute'
.measure { super }
gitlab/metrics/method_call.rb:36:in `measure'
retval = yield
...
(147 additional frame(s) were not displayed)
NoMethodError: undefined method `username' for nil:NilClass